Are Riser Studs/Nuts 3/8-16? Mercruiser 140

[myoldboat3]

GM Engine 140 HP 4-cyl 181 cu.in. s/n 3888148

What size are the studs/nuts that connect the riser to the manifold? They appear to be 3/8" but a new 3/8-16 SS nut didn't thread on. I would need my reading glasses to try to measure TPI. I was going to clean up the threads tonight but got rained out. I'd like to have the right hardware. The nuts I took off are fairly corroded and besides, I decorated my bilge with one of them and it's hiding from me.

I checked the manual but all it says is: Mercruiser 11-49838 NUT

EDIT: Came across an aftermarket part that says they are 3/8-24. Does that sound right?

Thanks.

 

[alk]

Yeah, if the 3/8th course thread didn’t fit, pretty safe bet that the 3/8 fine is what you need.

 

[myoldboat3]

I spent half an hour with some telescoping magnets but no luck. I did find a reference that said the elbow studs are 3/8-16 on the bottom (into the manifold) and 3/8-24 on the top (mounting nuts). So I'm picking up some 24 tpi nuts tomorrow.